Conventionally, a technology is known in which white lines of traffic lanes or parking places are recognized by utilizing images captured by image-capturing devices (cameras) mounted on a vehicle, so that the recognition results are utilized for lane recognition or parking frame detection. In such a technology, if raindrops, dirt, or the like are adhered to the image-capturing devices (cameras), the accuracy of recognizing white lines of traffic lanes or parking places is reduced and therefore the accuracy of lane recognition or parking frame detection is reduced. Thus, a variety of approaches for detecting adhesion of raindrops, dirt, or the like to the image-capturing devices (cameras) have been proposed (PTL1).